The disclosure relates to a method for circuit separation testing in a double gearwheel pump having the features of the disclosure. “Circuit separation testing” is intended to mean testing of leaktightness between the two gearwheel pumps of the double gearwheel pump or testing for leakage from one to the other gearwheel pump. The term “circuit separation testing” stems from the (possible) use of the double gearwheel pump in a hydraulic, slip-controlled vehicle brake system, in which each of the two gearwheel pumps is assigned to one brake circuit which are and must be separated from one another hydraulically.
German Offenlegungsschrift DE 10 2007 054 808 A1 discloses a double internal gearwheel pump having two internal gearwheel pumps which are arranged adjacent to one another on the same axis and have a common pump shaft for driving them. The two internal gearwheel pumps are arranged in a pump casing. The pump shaft is passed rotatably through a partition wall, which is arranged in the pump casing between the two internal gearwheel pumps and separates the two internal gearwheel pumps from one another. In the known double internal gearwheel pump, the partition wall is a separate component which is inserted into the pump casing and can also be interpreted as part of the pump casing. Integral formation of the partition wall with the pump casing or with part of the pump casing is also possible.
The pump shaft is sealed off in the partition wall by means of two axially spaced seals. A leakage duct which opens between the two seals carries off any leakage that may occur if one or both of the seals is leaky to a pump inlet of one of the two internal gearwheel pumps.
The known double internal gearwheel pump is provided for a hydraulic dual circuit vehicle brake system with a slip control system, such as ABS, ASR, ESP and/or FDR. Each of the two internal gearwheel pumps is arranged hydraulically in one of the two brake circuits. For reasons of functional reliability, “circuit separation” is absolutely essential. “Circuit separation” refers to hydraulic separation of the two brake circuits. Circuit separation in the double internal gearwheel pump can be nullified if the two internal gearwheel pumps are connected to one another hydraulically due to leakage, and this must absolutely be avoided. By means of the two seals which seal off the pump shaft in the partition wall of the pump casing of the double internal gearwheel pump, circuit separation is assured if at least one of the two seals is leaktight.